1. Field of the Invention
The invention relates to an apparatus for connection to a bus.
Such apparatuses are suitable for the energy supply for a bus which carries information and energy for bus subscribers. The apparatus is preferably used in a building automation installationxe2x80x94which is also referred to as a building management system. In the building automation installation a plurality of bus subscribers are generally connected together by way of a bus, in which respect a bus subscriber is by way of example a device for monitoring, controlling, and/or regulating process parameters such as for example room temperature, air humidity or brightness.
2. Description of the Prior Art
Decentrally fed buses are known, in which each bus subscriber is either a feeding or a non-feeding bus subscriber. Also known are centrally fed buses in which the bus feed is effected exclusively from a single central feed, while the other bus subscribers are non-feeding bus subscribers.
A bus subscriber node is known (EP 0 749 070 A) which has a feed module, a decision device and a measuring device for detecting the electrical current situation. The decision device decides automatically and only on the basis of the electrical current situation whether the feed module is or is not feeding the bus.
It has been found that bus systems with few subscriber nodes are advantageously fed decentrally but bus systems with relatively many subscriber nodes are more advantageously fed centrally. It is certainly realistic that, in the case of a bus system which varies in terms of the degree of expansion, as from a certain moment in time the nature of the feed is advantageously also to be adapted from central to decentral or vice-versa.
The object of the present invention is to propose a bus subscriber node for bus systems which can be fed centrally or decentrally, which node can be configured as a feeding or as a non-feeding bus subscriber node and can be implemented at low cost.
According to the present invention, there is provided apparatus for connection to a bus comprising
means for transmitting and/or receiving information by way of the bus,
a feed module,
a switch module which is actuatable by way of a switching logical member and by which the feed module can be connected to the bus or by which the feed module can be separated from the bus,
a monitoring member for detecting a current supplied by the feed module, and
a memory cell, wherein
the switching logical member is coupled to the memory cell and the monitoring member in such a way that the feed module can be separated from the bus on the basis of an item of information stored in the memory cell or on the basis of a certain current level detected by the monitoring member.
Advantageous features are set forth in the dependent claims.